Excitation-Wavelength-Dependent and Substrate-Dependent Photoluminescence From the Nonconjugated Polymeric Thin Film With Self-Assembly Nanoparticles

Abstract

Nonconjugated polymers have been synthesized from maleic anhydride, poly(ethylene glycol), and bisphenol-diglycidyl ether without utilizing any solvent. The polymeric thin films produced by the nonconjugated polymers were spin-coated on ITO coated glass and Si substrates. Self-assembly nanoparticles (1.6-6.2 nm) are observed. It is proposed that the nanoparticle is constructed through a self-assembly process with bisphenol-A aggregates and poly(ethylene glycol) moieties. The photoluminescence spectrum of the polymeric thin film on ITO peaks at near 450 nm that spans from 360 to 610 nm under 266 nm excitation. The polymeric thin film exhibits the excitation-wavelength-dependent photoluminescence that the emission peak shifts toward longer wavelength (about 11 nm) when the excitation wavelength increases from 266 to 325 nm, which is attributed to nanoparticle size distribution. Meanwhile, the substrate-dependent photoluminescence has been also observed that the PL peak of the polymeric thin film spin-coated on Si shows a blue shift (about 9 nm) compared with that on ITO, which probably arises from the dielectric screening. The highest occupied molecular orbital energy of the polymeric thin film is about -9.4 eV. The optical band gap is about 3.28 eV. The nonconjugated polymer is expected to use as a host material in optoelectronic applications.

Keywords

• Polymeric thin films
• photoluminescence
• self-assembly nanoparticles
• dielectric screening